Duration of vaginal bleeding and trisomy at prenatal diagnosis

In the case-control study of 118 women with autosomal trisomy identified at prenatal diagnosis and their 442 karyotypically normal matched controls, we found that there was no overall association between risk of trisomy and the presence of vaginal bleeding during pregnancy. However, a lengthy duration of bleeding appears to predict increased risk of trisorny.     

Amniotic fluid alpha-fetoprotein levels and prenatal diagnosis of autosomal trisomies

Pregnancies with fetal trisomy 21 have been associated with low amniotic fluid alpha-fetoprotein levels (AFAFP). This observation led to the suggestion that low AFAFP levels be used as a criterion for completion of a chromosomal analysis in patients who are not otherwise at increased risk for a fetal chromosome abnormality and in whom karyotyping might not have been completed for economic reasons. In order to assess the usefulness of such criteria, we reviewed the AFAFP levels of 90 cases of fetal trisomy 21, 23 cases of trisomy 18, and 10 cases of trisomy 13. These were compared with 2400 control samples with normal chromosome constitution. AFAFP levels were generally lower in pregnancies with trisomy 21, showing a median value of 0·72 MoM. However, 40 per cent of the trisomy 21 samples had AFAFP values greater than 0·8 MoM and 20 per cent were over 1·0 MoM. These data imply that over 50 per cent of Down syndrome cases might have been missed using a cut-off level of 0·70 MoM for completion of chromosome analysis. Using a higher cut-off level will leave only a small percentage of samples unkaryotyped. The distribution of AFP levels in trisomy 13 and 18 is no different from controls; we therefore believe that fetal karyotyping should be completed in every amniotic fluid sample obtained.     

First-trimester free beta (hCG) screening for Down syndrome

Maternal serum free beta (hCG) levels are elevated (median 2·20 MOM) in the first trimester of pregnancy in 38 Down syndrome cases as compared with appropriate controls. This observation may form the basis for its use as a marker in screening for Down syndrome in the first trimester. Altered levels of the free beta analyte are observed in pregnancy conditions or complications other than Down syndrome.     

Prenatal diagnosis for the detection of down syndrome: Why are so few eligible women tested?

Postpartum women ≧ 33 years were interviewed about their attitudes to and knowledge and use of prenatal diagnosis. Overall, 68 per cent had heard of prenatal diagnosis; nevertheless, only 30 per cent of those ≧ 35 had actually been tested. The only significant difference between eligible women who were tested and those who were not was maternal age. Of those tested, half requested it for themselves; conversely, only two-thirds of women requesting the procedure actually received it. Among women not tested, 82 per cent were never offered the procedure by the physician. Expressed attitudes to prenatal diagnosis were strongly positive among all women, with 75 per cent continuing to want testing after learning both their age-specific risk of having an affected child and the possible risks of amniocentesis. The data document a potential demand for amniocentesis far in excess of current use and present service facilities. They suggest, moreover, that underuse may reflect professional hesitation and underreferral more than consumer lack of demand or reluctance to be tested.     

Serum PAPP-A levels are depressed in women with fetal Down syndrome in early pregnancy

The value of maternal serum pregnancy-associated plasma protein (PAPP)-A in screening for Down syndrome in early pregnancy was assessed using stored samples. Seventeen cases of Down syndrome and 66 unaffected control pregnancies were studied. The median PAPP-A level in the cases was 0.42 multiples of the expected value in controls (p <0.0001). Eleven cases (65 per cent) had levels less than half the expected value compared with only six controls (9 per cent). A commercial assay kit is now needed so that prospective screening with this marker can begin.     

Serum PAPP-A measurements in first-trimester screening for Down syndrome

Serum PAPP-A measurements taken from 254 women in the first trimester are reported. Eleven chromosomal abnormalities were detected. The mean serum PAPP-A levels in cases of Down syndrome were 0.44 MOM at 9 weeks gestation, 0.15 MOM at 10 weeks, and 0.29 MOM at 11 weeks. The PAPP-A level at 10 weeks was below those of pregnancies which aborted spontaneously. At 11 weeks, the pregnancies with Down syndrome recorded the lowest PAPP-A levels at that gestation. On this small sample, offering chorionic villus sampling to women with singleton pregnancies and a PAPP-A level below 0.3 MOM (approximately 6.5 per cent of this at-risk group) would have detected all the Down syndrome fetuses at 10 weeks and 50 per cent at 11 weeks without selecting those cases destined to abort. This suggests that serum PAPP-A should continue to be investigated as a potential first-trimester screening test for Down syndrome.     

云南星云湖南岸生态整治规划

阐述了高原湖泊星云湖的自然条件、污染根源和景观特点,在此基础上通过本项目星云湖南岸(一期)生态整治规划,尝试在整个流域范围内运用GIS分析生态湿地建设、农业面源污染控制和重现滨水空间等,改善星云湖的水质,提高星云湖及周边的生态旅游价值.规划采用顶端控制和底端治理相结合的策略,恢复星云湖流域的生态功能,解决星云湖流域现有...     

Steel slags in a landfill top cover – Experiences from a full-scale experiment

A full scale field study has been carried out in order to test and evaluate the use of slags from high-alloy steel production as the construction materials for a final cover of an old municipal landfill. Five test areas were built using different slag mixtures within the barrier layer (liner). The cover consisted of a foundation layer, a liner with a thickness of 0.7 m, a drainage layer of 0.3 m, a protection layer of 1.5 m and a vegetation layer of 0.25 m. The infiltration varied depending on the cover design used, mainly the liner recipe but also over time and was related to seasons and precipitation intensity. The test areas with liners composed of 50% electric arc furnace (EAF) slag and 50% cementitious ladle slag (LS) on a weight basis and with a proper consistence of the protection layer were found to meet the Swedish infiltration criteria of ?50 l (m² a)^?1 for final covers for landfills for non-hazardous waste: the cumulative infiltration rates to date were 44, 19 and 0.4 l (m² a)^?1 for A1, A4 and A5, respectively. Compared to the precipitation, the portion of leachate was always lower after the summer despite high precipitation from June to August. The main reason for this is evapotranspiration but also the fact that the time delay in the leachate formation following a precipitation event has a stronger effect during the shorter summer sampling periods than the long winter periods. Conventional techniques and equipment can be used but close cooperation between all involved partners is crucial in order to achieve the required performance of the cover. This includes planning, method and equipment testing and quality assurance.     

贵州省部分地区土壤中酞酸酯类污染现状调查

对贵州省部分地区表层土壤中酞酸酯类的污染状况进行了调查。分别在遵义地区、黔南地区、黔东南地区和毕节地区采集483个土壤样品分析,结果表明,样品中酞酸酯总质量比(ΣPAEs)为未检出~8.22 mg/kg,均值为0.63 mg/kg。其中DEHP和DBP为主要污染物,均值分别为0.32 mg/kg和0.24 mg/kg,检出率分别为90.89%和97.10%。